A computer is known to comprise a central processing unit, system memory, peripheral ports, audio processing circuitry, and video processing circuitry. The peripheral ports enable the central processing unit to communicate with peripheral devices such as printers, monitors, the Internet, external tape drives, etc. The video graphics circuitry functions as a co-processor to the central processing unit for processing video data and/or graphics data. Typically, the video graphics circuitry includes a graphics core that processes the graphics data and a video core that processes the video data. As is also known, graphics data is generated by the central processing unit while executing computer applications and video data is received via a tuner from a television broadcast, cable broadcast, satellite broadcast, VCR, DVD player, etc.
The video graphics processor mixes the processed graphics data and the processed video data to produce a mixed resultant, which is provided to a digital to analog converter (DAC). The DAC converts the mixed resultant into an analog signal and provides the analog signal to a frame buffer for storage and subsequent display. As is known, the bit size of the processed graphics data, the processed video data, and the mixed resultant is at least partially based on a cost-performance tradeoff of the video core, graphics core, and the DAC. Currently, for commercial grade video graphics processors, the cost-performance tradeoff dictates an 8-bit data size for the processed graphics data, the processed video, and the miixed resultant. In particular, 8-bits was chosen because 8-bit DACs are relatively inexpensive and many graphics applications use 8-bit RGB data.
A performance tradeoff for using 8-bit data is a degradation of the reconstructed analog video signal. As is known, the tuner digitizes and quantizes the received analog video signal based on the bit size of the data. The quantization causes the degradation by digitally rounding off the representation of the analog signal. The rounding off causes some loss in the detail of the analog signal. The 8-bit data size keeps the loss of detail to a relatively low level, but the loss is noticeable to some viewers. As is also known, the amount of quantization decreases, hence the degradation decreases, as the number of bits of the data size is increased. Cost and compatibility with graphics data have kept the video core at an 8-bit data size.
The cost of higher data size DACs have recently dropped, thus making it a commercially viable option to use a 10 bit DAC in a video graphics processor. With a larger data size DAC, the amount of quantization would be reduced, thereby reducing degradation of video signals. While a 10-bit DAC would enable the development of a higher quality video core, the resulting 10-bit video data would be is incompatible with the 8-bit graphics data. As one can image, this incompatibility issue will continue well beyond the 10-bit and 8-bit incompatibility since the graphics art and digital-to-analog conversion art are separate and distinct arts. Thus, each art will advance at different paces.
Therefore, a need exists for a method and apparatus that allow incompatibility of graphics data and video data within a video graphics processor.